Thymidine kinase

Thymidine kinase (TK) catalyzes the conversion of deoxythymidine (THM) to deoxythymidine 5’-phosphate (THMP) with the coversion of ATP to ADP. TK has an important role in the synthesis of DNA. It is required for the action of many antiviral drugs. Higher organisms have 2 isozymes. TK1 is cell cycle-dependent while TK2 is found in the mitochondria and is cell cycle-independent. TK undergoes feed-back regulation by thymidine triphosphate (TTP). Adenosyl-thymidyl-tetraphosphate (TP4A) is a bisubstrate inhibitor of TK.

3D Structures of thymidine kinase
2e2h – HsvTK – Herpes simplex virus 1 3e2i – TK – Staphylococcus aureus 2qpo – TmTK – Thermotoga maritima

Thymidine kinase complex with reactants or products
1e2i - HsvTK + hydroxypropyladenine 1e2j - HsvTK (mutant) + THM 1kim - HsvTK + THM 1vtk - HsvTK + THMP + ADP 2vtk - HsvTK + THM + ADP 3vtk - HsvTK + substrate analog + ADP 3f0t, 1of1 – HsvTK residues 45-376 + thymine derivative  1qhi, 1ki3, 1ki5, 1ki2, 1ki4 - HsvTK + inhibitor 1e2p, 1e2m, 1e2n, 1e2k, 1e2l, 1ki6, 1ki7, 1ki8 – HsvTK + substrate analog 1osn – TK + inhibitor + ADP - Human Herpes virus 3 1p6x – EhvTK + THM – Equine Herpes virus 4 1p72 - EhvTK + THM + ADP 2qqe – TmTK + THM 2qq0– TmTK + THM + ADP + THMP + ANP 2b8t - TK + THM – Ureaplasma parvum<BR /> 2j9r – TK + THM – Bacillus anthracis<BR /> 1xx6 – TK + ADP – Clostridium acetobutylicum

Thymidine kinase complex with feed-back inhibitor
2j87 – TK + TTP – Vaccinia virus<BR /> 2uz3 – TK (mutant) + TTP – Ureaplasma urealyticum<BR /> 2ja1 – TK + TTP – Bacillus cereus

Thymidine kinase complex with bisubstrate inhibitor
1p7c – HsvTK + TP5A<BR /> 1p73 - EhvTK + TP4A<BR /> 1p75 - EhvTK + TP5A<BR /> 2orw – TmTK + TP4A<BR />

Thymidine kinase 1
1xbt - hTK1 residues 1-193 – human<BR /> 2wvj – hTK1 residues 1-193 (mutant) + TTP<BR /> 2orv – hTK1 (mutant) + TP4A<BR />

Thymidine kinase 2
1w4r – hTK2 + TTP